Tolerance is the range within which a certain parameter must fall. For example, a hole must be drilled 35 mm in diameter, with a tolerance of +/- 1 mm. So the hole could be 34 mm to 36 mm and still be within specified tolerance.
Accuracy is usualy given in Per Cent. A hole of 35 mm with an accuracy of +/- 3% would mean that the hole could be 35 + (.03 x 35), or 35 - (.03 x 35), or 33.95 to 36.05 mm in diameter.